Heat pump system

ABSTRACT

In a heat pump system, a dual diameter, double-acting free piston apparatus is utilized as an expander-compressor. Working fluid is compressed in the large diameter portion of the free piston apparatus and is directed to a condenser. Part of the working fluid flowing from the condenser is directed through an expansion valve and an evaporator, and is then alternately admitted to the opposite ends of the large diameter portion of the free piston apparatus. The remainder of the working fluid flowing from the condenser is directed through a pump and a boiler and is then alternately admitted to the small diameter portions of the free piston apparatus, whereupon the working fluid is expanded to effect actuation of the apparatus. The flow of high temperature, high pressure working fluid into the small diameter portions of the free piston apparatus is controlled by disk valves which also function to direct spent working fluid from the small diameter portions of the free piston apparatus to the condenser. The free piston apparatus further comprises a housing which forms a hermetic seal enclosing all of the reciprocating and rotating components of the system.

United States Patent [1 1 Golds berry HEAT PUMP SYSTEM [75] Inventor:Fred L. Goldsberry, Dallas, Tex.

[73] Assignee: Lone Star Gas Company, Dallas,

Tex.

[22] Filed: Mar. 1, 1973 [21] Appl. No.: 337,131

[52] U.S. Cl 62/115, 62/116, 62/467, 62/498, 62/500, 60/36, 417/396,417/404 [51] Int. Cl. F25b l/00 [58] Field of Search 62/115, 116,467,498, 62/500, DIG. 2; 417/396 X, 403, 404 X; 60/24, 36 X [56]References Cited UNITED STATES PATENTS 2,204,040 7/1940 Pierotti et a1.62/323 X 2,441,632 7/1961 Rogers 62/467 2,637,981 5/1953 Russell 62/501X 2,986,898 6/1961 Wood, Jr. 417/404 2,986,907 6/1961 Hoop 62/116 x2,992,636 7/1961 Sampie'tro 91/305 3,137,144 6/1964 Kaufman et a1.62/141 3,710,586 Maudcin 62/498 X Primary Examiner-William F. ODeaAssistant Examiner-Peter D. Ferguson Attorney, Agent, or Firm-Richards,Harris & Medlock [111 3,861,166 [451 Jan. 21 1975 57] ABSTRACT In a heatpump system, a dual diameter, double-acting free piston apparatus isutilized as an expandercompressor. Working fluid is compressed in thelarge diameter portion of the free piston apparatus and is directed to acondenser. Part of the working fluid flowing from the condenser isdirected through an expansion valve and an evaporator, and is thenalternately admitted to the opposite ends of the large diameter portionof the free piston apparatus. The remainder of the working fluid flowingfrom the condenser is directed through a pump and a boiler and is thenalternately admitted to the small diameter portions of the free pistonapparatus, whereupon-the working fluid is expanded to effect actuationof the apparatus. The flow of high temperature, high pressure workingfluid into the small diameter portions of the free piston apparatus iscontrolled by disk valves which also.

function to direct spent working fluid from the small diameter portionsof the free piston apparatus to the condenser. The free piston apparatusfurther comprises a housing which forms a hermetic seal enclosing all ofthe reciprocating and rotating components of the system.

19 Claims, 1 Drawing Figure HEAT PUMP SYSTEM BACKGROUND AND SUMMARY OFTHE INVENTION This invention relates to heat pump systems, and moreparticularly to a heat pump system utilizing a dual diameter,double-acting free piston apparatus as an expander-compressor.

Commercially available refrigerators and similar heat pump systems haveheretofore usually been either of the compression type or the absorptiontype. The compression type system typically employs an electric motor tooperate a compressor. By this means a refrigerant is forced from thecompressor through a condenser, through an expansion valve, through anevaporator and back to the compressor. In the absorption typerefrigerator a fuel such as natural gas is utilized to boil arefrigerant out of a carrier liquid. The refrigerant is directed througha condenser and an evaporator and then is recombined with the carrierliquid in an absorber.

Heat pump systems of the compression type utilizing a fuel such asnatural gas as the basic energy source have also been providedheretofore. Such systems have employed both turbines and free pistons asexpanders for high temperature, high pressure working fluid. Onedifficulty that has often been experienced in the use of these systemsinvolves the lack of a hermetic seal surrounding the reciprocatingand/or rotating components. This permits leakage of the working fluid atvarious sliding and rotating seals, and thereby necessitates relativelyfrequent maintenance of the system merely to replenish the workingfluid.

The present invention relates to a heat pump system wherein a dualdiameter, double-acting free piston apparatus is utilized both as aworking fluid expander and as a working fluid compressor. In accordancewith the broader aspects of the invention, working fluid is partiallycompressed in the large diameter portion of the free piston apparatusand is then directed through a condenser. Part of the working fluidflowing from the condenser is directed through an expansion valve and anevaporator, and is then alternately admitted to the opposite ends of thelarge diameter portion of the free piston apparatus. The remainder ofthe working fluid flowing from the condenser is directed through a pumpand a boiler, and is then alternately admitted to opposed small diameterportions of the free piston apparatus, wherein the working fluid isexpanded to effect reciprocation of the free piston. Spent working fluidfrom the small diameter portions of the free piston apparatus isreturned to the condenser.

In accordance with other aspects of the invention, the flow of workingfluid through the small diameter portions of the free piston apparatusis controlled by rotating disk valves. The valves are rotated by aninduction motor which may also be utilized to drive the pump. Therequired phase relationship between the disk valves is maintained by atiming rod interconnecting the valves and extending through the freepiston.

In accordance with still other aspects of the invention, the free pistonapparatus includes a housing defining a dual diameter cylinder whichreceives the free piston. The housing also encloses the disk valves, theinduction motor, and the pump. That is, the housing effects a hermeticseal enclosing all of the working components of the heat pump system.Such a seal is useful in substantially reducing the loss of the workingfluid which normally occurs at rotating and sliding seals. This in turnsubstantially reduces the frequency of maintenance which is necessary inthe use of the present invention as compared with prior heat pumpsystems.

DESCRIPTION OF THE DRAWING A more complete understanding of theinvention may be had by referring to the following Detailed Descriptionwhen taken inconjunction with the accompaning DRAWING, wherein a heatpump system incorporating the invention is schematically illustrated.

DETAILED DESCRIPTION Referring now to the Drawings, a heat pump system10 incorporating the invention is schematically illustrated. The heatpump system 10 comprises a dual diameter, double-acting free pistonapparatus 12 includ ing a housing 14. The housing 14 comprises a dualdiameter, double-ended cylinder and includes a central,

relatively large diameter cylindricalportion l6 and opposed relativelysmall diameter cylindrical portions 18. The small diameter portions 18are equal in length and are coaxial with the large diameter port-ion 16.

The free piston assembly 12 further includes a free piston 20 which ismounted in the cylinder of the housing 14 for reciprocation with respectthereto. The free piston 20 comprises a dual diameter, double-actingpiston and includes a relatively large diameter portion 22 whichreciprocates in the large diameter portion of the cylinder and opposedrelatively small diameter portions 24 which reciprocate in the smalldiameter portions of the cylinder. The small diameter portions 24 of thefree piston are coaxial with the large diameter portion 22 and are equalin length. The free piston 20 is provided with suitable piston rings 26adapted for cooperation with the interior walls of the housing 14 toeffect sliding seals.

The heat pump system 10 is charged with a suitable working fluid, suchas FREON lll, FREON l 12, FREON l 13, etc. Low pressure, relatively warmworking fluid is alternatively received in the opposite ends of thelarge diameter portion 16 of the housing 14 through a line 28 and a pairof suitable check valves 30. Thus, upon reciprocation of the free piston20, the working fluid is simultaneously partially compressed in one endof the large diameter portion 16 and is simultaneously drawn into theopposite end. The relatively warm, partially compressed working fluidthen flows out of the cylinder 14 through a pair of check valves 32 anda line 34.

The arrangement of the inlet and outlet portions relative to the sideand end walls of the large diameter portion 16 of the housing 14comprises an important feature of the invention. That is, since theoutlet ports are arranged in the side walls, one of the outlet ports isclosed by the free piston 20 at the terminus of each reciprocationthereof. By this means a quantity of working fluid is trapped in the endof the large diameter portion 16, thereby providing the fluid cushionwhich functions to decelerate the piston. This in turn assures that theterminus of each reciprocation of the free piston 20 will be smooth andthat the piston is not forcefully driven into engagement with eitherendof the cylinder l4.

The line 34 extends to a condesner 36. A blower 38 or equivalentapparatus is provided for directing a secondary fluid such as airthrough the condenser 36, thereby cooling the working fluid by heattransfer to the secondary fluid. The condenser 36 and the blower 38preferably have sufficient capacity that the working fluid istransformed from the gaseous phase to the liquid phase within thecondenser 36. As will be apparent to those skilled in the art, in thecase of an air conditioning system, a refrigeration system, or the like,both the free piston apparatus 12 and the condenser 36 will be locatedoutside of a zone to be cooled.

Relatively high pressure, relatively low temperature working fluid inthe liquid phase flows from the condenser 36 through a line 40. Part ofthe working fluid flowing from the condenser 36 is directed through anexpansion valve 42. The valve 42 functions to substantially reduce thepressure of, and thereby simultaneously substantially cool the workingfluid. The low temperature, low pressure working fluid flowing from thevalve 42 is directed through an evaporator 44 wherein the working fluidreturns to the gaseous phase.

In the case of an air conditioning system, a refrigeration system, orthe like, the evaporator 44 is positioned within or at least in directcommunication with the zone to be cooled. A blower 46 or equivalentapparatus directs a secondary fluid such as air through the evaporator44. By this means heat transfer between the secondary fluid and theworking fluid is effected, whereby the secondasry fluid is cooled, andthe working fluid is partially heated. Low pressure, relatively warmworking fluid flowing from the evaporator 44 is directed to the largediameter portion 16 of the cylinder 14 through the line 28.

The remainder of the liquid phase working fluid flowing from thecondenser 36 through the line 40 is directed to a gear pump 48. The pump48 is driven by an induction motor 50 and functions to substantiallypressurized the working fluid flowing therethrough. The high pressureworking fluid flowing from the pump 48 is directed through a check valve51 and a line 52 to a boiler 54. In the case of a refrigerator, an airconditioner, or the like, both the pump and the boiler are locatedoutside of the zone to be cooled.

The boiler 54 is actuated by a gas burner 56 and functions tosubstantially heat the working fluid. High pressure, high temperatureworking fluid flows from the boiler 54 in the gaseous phase through aline 57. Working fluid from the line 57 is alternately admitted to thesmall diameter portions 18 of the cylinder 14 by means of a pair of diskvalves 58. Each valve 58 functions to admit high temperature, highpressure working fluid to the adjacent small diameter portion 18 of thecylinder 14 during travel of the free piston 20 away from the valve inquestion, and to release spent working fluid from the adjacent smalldiameter portion 18 of the cylinder during travel of the free pistontoward the valve in question. Spent working fluid from the smalldiameter portions 18 of the cylinder 14 passes through a line 60 whichextends to the line 34 and hence to the condenser 36.

The disk valves 58 of the free piston assembly 12 are maintained in apredetermined angular phase relationship with respect to each other by ashaft 62 which interconnects the valves. The shaft 62 extends throughthe free piston 20 along the axis thereof and a passageway of sufficientclearance is provided in the free piston to permit reciprocation of thepiston relative to the shaft. The shaft 62 and the disk valves 58 arerotated by the induction motor 50 which drives the gear pump 48. In theevent that it is desired to rotate the disk valves 58 at a differentspeed from that of the gear pump 48, a suitable transmission 64 may beprovided.

It will thus be understood that in the operation of the heat pump system10, the energy of the high temperature, high pressure working fluidflowing from the boiler 54 is utilized to reciprocate the free piston 20within the housing 14. During the initial portion of each reciprocation,energy from the working fluid is im parted to the free piston.Thereafter, both energy from the working fluid and the momentum of thefree piston cause the piston to complete the reciprocation. By thismeans working fluid is compressed in the large diameter portion 16, andspent working fluid is expelled from the opposite small diameter portion18. At the terminus of each reciprocation, the outlet port in the largediameter portion 16 is closed by the piston, whereupon trapped workingfluid functions to decelerate the piston before it engages the adjacentend of the housing. The piston is then ready for reciprocation in theopposite direction.

The heat pump system 10 further includes a number of components whichfunction to provide control over the operation of the system and whichare actuated by a suitable power source (not shown). For example, apressure switch 65 is provided for actuating a start/stop switch 66 toterminate operation of the system in the event of an inadequate pressuredrop across the expansion valve 42. The pressure switch 65 may be of thetype manufactured by the Powers Regulator Co. of Skokie, Illinois underModel Number SW1 34-1450 A65. Both the expansion valve 42 and the blower46 are operated under the control of a thermostat 68 whereby the outputof the heat pump system 10 may be regulated.

A pressure responsive switch 70 is provided for monitoring the pressurewithin each small diameter portion 18 at the terminus of the travel ofthe small diameter portions of the free piston 20 therein. The switch 70controls the operation of a throttle valve 72 and thereby regulates theflow of high temperature, high pressure working fluid through the line57 and into the small diameter portions 18 of the cylinder 14. By thismeans dissipation of the entire energy of the working fluid entering thesmall diameter portions of the cylinder during each reciprocation of thefree piston is assured, thereby preventing a pop when the disk valvesare opened. The switch 70 may be of the type manufactured and sold byPowers Regulator Co. as Model Number SWI 34-1455, and the throttle vavle72 may be a motor actuated two-way single seat valve of the typemanufactured and sold by Powers Regulator Co.

The boiler 54 is provided with a float controlled switch 74 which isresponsive to the level of liquid working fluid within the boiler. Theswitch 74 operates a bypass valve 76 which functions to return at leasta portion of the output of the gear pump 48 to the inlet thereof. Bythis means a predetermined level of liquid working fluid within theboiler 54 is assured. The switch 74 may be of the type supplied byMcDonnel & Miller Inc., of Chicago, Illinois under Model Number 150.

The gas burner 56 of the boiler 54 is provided with a pressure actuatedgas valve 78. The valve 78 is also responsive to a high temperaturelimit switch including a temperature responsive member 80 positionedwithin the boiler 54. By this means operation of the gas burner 56 isterminated in the event that either the pressure or the temperaturewithin the boiler 54 exceeds a predetermined limit. The valve 78 may beof the type manufactured and sold by Honeywell Inc. of Minneapolis,Minnesota as a v58194E Powerpile combination gas control valve.

One of the important features of the heat pump system is the fact thatthe housing 14 encloses all of the reciprocating and rotating componentsof the system. That is, the housing 14 hermetically seals the freepiston 20, the disk valves 58, the pump 48 and the apparatus foractuating the same. By this means loss of working fluid from the systemis completely prevented.

It will of course be appreciated that the heat pump system 10incorporates certain sliding and rotating seals. However, since all ofthe working components of the system are enclosed by the housing 14, anyflow of working fluid around such seals merely causes the working fluidto enter another portion of the system. While such flow may cause acertain loss of operating efficiency in the system, there is absolutelyno'loss of working fluid. This is important in eliminating a problemthat has been encountered in the use of prior art heat pump systems,wherein periodic maintenance has been required merely to replenish theworking fluid.

The embodiment of the heat pump system 10 illustrated in the Drawingutilizes the same motor 50 to actuate the pump 48 and the disk valves58. As will be apparent to those skilled in the art, an alternativeconstruction may be provided wherein separate motors are utilized todrive the pump and to rotate the valves. In such cases, the housing 14may enclose only the motor which actuates the disk valves, and aseparate housing may be provided for enclosing the pump and itsoperating motor. Such an alternative construction does not, however,deviate from the basic concept of providing a hermetic seal extendingaround all of the reciprocating and rotating components of the heat pumpsystem.

From the foregoing, it will be understood that the present inventioncomprises a heat pump system utilizing a dual diameter, double-actingfree piston apparatus as an expander-compressor. The system is furthercharacterized by the use of a fuel such as natural gas as the basicenergy source. A highly advantageous characteristic of the system isthat the reciprocating and rotating components thereof are entirelyenclosed in a hermetic seal, thereby preventing loss of the workingfluid utilized in the system.

Although specific embodiments of the invention have been illustrated inthe Drawing and described in the foregoing Detailed Description, it willbe understood that the invention is not limited to the embodimentsdisclosed, but is capable of numerous rearrangements, modifications, andsubstitutions of parts and elements without departing from the spirit ofthe invention.

What is claimed is:

1. In combination with a heat pump system wherein a secondary fluid iscooled by contact with an evaporator supplied with working fluid from acondenser, the improvement which comprises:

a boiler adapted to provide the working fluid at a high pressure andtemperature:

a housinghaving first and second pairs of opposed chambers with a dualradius piston therein having oppositely directed faces;

structure forming a first fluid path connected from said boileralternately to apply high pressure gas from said boiler to theoppositely directed faces of said piston in said first opposed chambersin said housing to reciprocate said piston;

structure forming a second path connected from the evaporatoralternately to apply low pressure gas to saidsecond pair of opposedchambers to deliver compressed fluid from the evaporator to the condenser;

valve means within said housing for controlling alternate admission offluid from said first fluid path to the oppositely directed faces ofsaid piston in said first opposed chambers and directing spent fluidfrom said chambers ofsaid pistons to the condenser, said valve meanscomprising rotating disk valves driven by motor means and disposedadjacent the first opposed chambers in said housing with a shaftextending through said piston for maintaining a predetermined angularphase relationship between the valves; and

structure forming a third path connected from the condenser to saidboiler for supplying working fluid to said boiler.

2. The system according to claim 1 wherein said housing forms a hermeticseal which encloses said piston and the valve means.

3. The system according to claim 1 further including an expansion valvefor directing fluid from the condenser to the evaporator and a pump fordirecting fluid from the condenser to said boiler.

4. A heat pump system comprising:

a housing having a dual diameter cylinder including a central relativelylarge diameter portion and concentric relatively small diameter portionsextending axially from the opposite ends of the large diameter portion;

a dual diameter free piston including a central relatively largediameter portion received in the large diameter portion of said cylinderand relatively small diameter portions extending from the opposite endsof the relatively large diameter portion into the small diameterportions of said cylinder;

an evaporator adapted to effect heat transfer between a working fluidand a secondary fluid;

means for directing low pressure, relatively warm working fluid flowingfrom said evaporator into the relatively large diameter portion of saidcylinder partially to compress the working fluid upon reciprocation ofthe free piston;

a condenser adapted to effect heat transfer between said working fluidand a third fluid;

means for directing relatively high pressure, relatively warm workingfluid from the large diameter portion of said cylinder to said condenserto cool the working fluid;

an expansion valve;

means for directing part of the relatively high pressure, relativelycool working fluid flowing from said condenser through said expansionvalve simultaneously substantially to reduce the pressure andtemperature of said working fluid;

means for directing the low temperature, low pressure working fluid fromsaid expansion valve through saidevaporator to cool the second fluid byheat transfer to said working fluid;

a pump;

means for directing the remainder of the relatively cool, relativelyhigh pressure working fluid from said condenser to said pumpsubstantially to increase the pressure of said working fluid;

a boiler;

means for directing the high pressure, relatively low temperatureworking fluid flowing from said pump to said boiler substantially toheat said working fluid;

a pair of disk valves mounted within said housing adjacent the oppositeends of the small diameter portions of said cylinder for alternately andcyclically directing the high pressure, high temperature working fluidflowing from said boiler to the opposed small diameter portions of saidcylinder to reciprocate said free piston therein and means for directingspent working fluid from said small diameter portions of said cylindermeans to said condenser; and

means for rotating said disk valves in synchronism to control flow ofworking fluid alternately through the small diameter portions of saidcylinder.

5. The heat pumping system according to claim 4 wherein the disk valvesare rotated in synchronism by a shaft extending between the valves andthrough the free piston.

6. The heat pump system according to claim 5 wherein said cylinder formsa hermetic seal enclosing at least said free piston, said disk valves,and said valve rotating means.

7. The heat pump system according to claim 4 further including meansresponsive to the level of working fluid within the boiler forselectively bypassing high pressure, relatively low temperature workingfluid flowing from the outlet of said pump to the inlet of said pump.

8. A heat pump system comprising:

a free piston including a relatively large diameter portion andconcentric relatively small diameter portions extending coaxially fromthe opposite ends of the large diameter portions;

cylinder means surrounding the free piston and including a centralrelatively large diameter portion for receiving the large diameterportion of said free piston and opposed relatively small diameterportions for receiving the small diameter portions of said piston;

a pair of disk valves mounted in said cylinder means adjacent toopposite ends of said small diameter portions thereof;

means for rotating said disk valves in synchronism for alternate flow ofworking fluid into and out of the small diameter portions of saidcylinder means to reciprocate said free piston within said cylindermeans;

said cylinder means forming a hermetic seal which encloses at least saidfree piston, said disk valves, and said valve rotating means;

a condenser;

a pump;

means for directing part of the working fluid flowing from saidcondenser to said pump substantially to pressurize said working fluid;

a boiler;

means for directing at least part of said working fluid flowing fromsaid pump to said boiler substantially to heat said working fluid;

means for directing spent working fluid flowing out of said smalldiameter portions of said cylinder means under control of said diskvalves to the condenser;

an expansion valve;

means for directing the remainder of said working fluid flowing fromsaid condenser through said expansion valve and substantially to reducethe pressure and temperature of said working fluid;

an evaporator for flow of low pressure, low temperature working fluidflowing from said expansion valve to cool a secondary fluid by heattransfer to said working fluid;

means for alternately admitting working fluid flowing from saidevaporator intothe opposite ends of the large diameter portion of thecylinder means partially to compress the working fluid; and

means for directing compressed working fluid flowing from the largediameter portion of said cylinder means to said condenser.

9. The heat pump system according to claim 8 wherein the valve rotatingmeans comprises:

an induction motor including a rotor enclosed by said cylinder means;and

a shaft extending through said free piston along the axis thereof forinterconnecting said disk valves and thereby maintaining a predeterminedangular phase relationship between said valves.

10. The heat pump system according to claim 8 further including meansresponsive to the pressure within the small diameter portions of saidcylinder at the terminus of each reciprocation of the free pistontherein for regulating the flow of high pressure, high temperatureworking fluid into the small diameter portions of said cylinder means.

11. The heat pump system according to claim 10 further including meansresponsive to the level of working fluid within said boiler forrecirculating a portion of the pump output to the inlet thereof.

12. A heat pumping process comprising:

alternately receiving low pressure, relatively warm working fluid froman evaporator in the opposite ends of the large diameter portion of adual diameter, double-acting free piston assembly and thereby partiallycompressing the working fluid;

directing the partially compressed working fluid from the large diameterportion of the free piston assembly through a condenser and therebypartially cooling the working fluid; directing a portion of thepartially cooled working fluid flowing from the condenser through anexpansion valve and thereby simultaneously substantially reducing thepressure of and substantially cooling the working fluid; directing thelow pressure, low temperature working fluid flowing from the expansionvalve through the evaporator and thereby cooling a secondary fluid;

directing the remainder of the partially cooled working fluid flowingfrom the condenser through a pump and thereby substantially compressingthe working fluid;

directing the high pressure working fluid flowing from the pump througha boiler and thereby substantially heating the working fluid;

alternately admitting the high temperature, high pressure working fluidfrom the boiler to the opposed small diameter portions of the freepiston assembly by means of rotating disk valves located at the oppositeends of the free piston assembly and thereby reciprocating the freepiston;

releasing the spent working fluid from the small diameter portions ofthe free piston through said rotating disk valves; and

directing the spent fluid to the condenser.

13. The heat pumping process according to claim 12 wherein the steps ofadmitting high temperature, high pressure working fluid to the oppositeends of the small diameter portion of the free piston assembly anddirecting spent working fluid from the free piston assembly to thecondenser are further characterized by simultaneously rotating the diskvalves located at the opposite ends of the free piston assembly by meansof a rod extending through the free piston and interconnecting the twodisk valves.

14. The heat pumping processing according to claim 12 furthercharacterized by the step of regulating the rate of fluid flow from theboiler into the opposite ends of the small diameter portions of the freepiston assembly in accordance with the pressure of the spent workingfluid within the small diameter portions of the free piston assembly atthe end of each reciprocation of the free piston.

15. The heat pumping process according to claim 12 wherein the step ofdirecting the high pressure working fluid flowing from the pump througha boiler is further characterized by returning a portion of the pumpoutput to the input thereof in accordance with the level of workingfluid within the boiler.

16. A heat pumping process comprising: cooling relatively high pressure,relatively warm working fluid in a condenser;

substantially reducing the pressure of and thereby substantially coolingpart of the relatively high pressure, relatively low temperature workingfluid flowing from the condenser in an expansion valve;

partially heating the low temperature, low pressure working fluidflowing from the expansion valve in an evaporator and therebysubstantially cooling a secondary fluid;

partially compressing the low pressure, relatively warm working fluidflowing from the evaporator in the large diameter portion of a dualdiameter, double-acting free piston apparatus;

directing the partially compressed, relatively warm working fluid fromthe large diameter portion of the free piston apparatus to thecondenser;

substantially pressurizing the remainder of the rela- I tively highpressure, relatively cool working fluid flowing from the condenser in apump;

substantially heating the high pressure, relatively low temperatureworking fluid flowing from the pump in a boiler;

rotang disk valves at the opposite ends of the small diameter portion ofthe free piston assembly and thereby cyclically admitting the hightemperature, high pressure working fluid flowing from the boiler toopposed small diameter portions of the free piston apparatus toreciprocate the free piston;

rotating said disk valves at the opposite ends of the small diameterportion of the free piston assembly and releasing spent working fluidthrough said disk valves from the small diameter portions of the freepiston apparatus; and

returning the spent working fluid to the condenser.

17. The heat pumping process according to claim 16 wherein the step ofrotating disk valves at the opposite ends of the small diameter portionof the free piston assembly is further characterized by maintaining thedisk valves in synchronism by means of a rod interconnecting the diskvalves and extending through the free piston of the free pistonapparatus.

18. The heat pumping process according to claim 16 wherein the step ofadmitting high temperature, high pressure working fluid from the boilerto the small diameter portions of the free piston apparatus is furthercharacterized by monitoring the pressure within the small diameterportions of the free piston apparatus at the end of each reciprocationof the free piston and regulating the flow of high temperature, highpressure fluid into the small diameter portions of the free pistonassembly in accordance with such pressure.

19. A heat pump system comprising:

a housing having a dual diameter cylinder including a central relativelylarge diameter portion and concentric relatively small diameter portionsextending axially from the opposite ends of the large diameter portion;

a dual diameter free piston including a central relatively largediameter portion received in the large diameter portion of said cylinderand relatively small diameter portions extending from the opposite endsof the relatively large diameter portion into the small diameterportions of said cylinder;

an evaporator adapted to effect heat transfer between a working fluidand a secondary fluid;

means for directing low pressure, relatively warm working fluid flowingfrom said evaporator into the relatively large diameter portion of saidcylinder partially to compress the working fluid upon reciprocation ofthe free piston;

a condenser adapted to effect heat transfer between said working fluidand a third fluid;

means for directing relatively high pressure, relatively warm workingfluid from the large diameter portion of said cylinderto said condenserto cool the working fluid;

an expansion valve;

means for directing part of the relatively high pressure, relativelycool working fluid flowing from said condenser through said expansionvalve simultaneously substantially to reduce the pressure andtemperature of said working fluid;

means for directing the low temperature, low pressure working fluid fromsaid expansion valve through said evaporator to cool the secondary fluidby heat transfer to said working fluid;

a pump;

means for directing the remainder of the relatively cool, relativelyhigh pressure working fluid from said condenser to said pumpsubstantially to increase the pressure of said working fluid;

a boiler;

means for directing the high pressure, relatively low temperatureworking fluid flowing from said pump to said boiler substantially toheat said working fluid;

means located within said housing for alternately and cyclicallydirecting the high pressure, high temperature working fluid flowing fromsaid boiler to the opposed small diameter portions of said cylinder toreciprocate said free piston therein;

means responsive to pressures within the small diameter portions of saidcylinder at the terminus of each stroke of said free piston forcontrolling the flow of high pressure, high temperature working fluidinto said small diameter portions of said cylinsaid cylinder means tosaid condenser.

1. In combination with a heat pump system wherein a secondary fluid iscooled by contact with an evaporator supplied with working fluid from acondenser, the improvement which comprises: a boiler adapted to providethe working fluid at a high pressure and temperature: a housing havingfirst and second pairs of opposed chambers with a dual radius pistontherein having oppositely directed faces; structure forming a firstfluid path connected from said boiler alternately to apply high pressuregas from said boiler to the oppositely directed faces of said piston insaid first opposed chambers in said housing to reciprocate said piston;structure forming a second path connected from the evaporatoralternately to apply low pressure gas to said second pair of opposedchambers to deliver compressed fluid from the evaporator to thecondenser; valve means within said housing for controlling alternateadmission of fluid from said first fluid path to the oppositely directedfaces of said piston in said first opposed chambers and directing spentfluid from said chambers of said pistons to the condenser, said valvemeans comprising rotating disk valves driven by motor means and disposedadjacent the first opposed chambers in said housing with a shaftextending tHrough said piston for maintaining a predetermined angularphase relationship between the valves; and structure forming a thirdpath connected from the condenser to said boiler for supplying workingfluid to said boiler.
 2. The system according to claim 1 wherein saidhousing forms a hermetic seal which encloses said piston and the valvemeans.
 3. The system according to claim 1 further including an expansionvalve for directing fluid from the condenser to the evaporator and apump for directing fluid from the condenser to said boiler.
 4. A heatpump system comprising: a housing having a dual diameter cylinderincluding a central relatively large diameter portion and concentricrelatively small diameter portions extending axially from the oppositeends of the large diameter portion; a dual diameter free pistonincluding a central relatively large diameter portion received in thelarge diameter portion of said cylinder and relatively small diameterportions extending from the opposite ends of the relatively largediameter portion into the small diameter portions of said cylinder; anevaporator adapted to effect heat transfer between a working fluid and asecondary fluid; means for directing low pressure, relatively warmworking fluid flowing from said evaporator into the relatively largediameter portion of said cylinder partially to compress the workingfluid upon reciprocation of the free piston; a condenser adapted toeffect heat transfer between said working fluid and a third fluid; meansfor directing relatively high pressure, relatively warm working fluidfrom the large diameter portion of said cylinder to said condenser tocool the working fluid; an expansion valve; means for directing part ofthe relatively high pressure, relatively cool working fluid flowing fromsaid condenser through said expansion valve simultaneously substantiallyto reduce the pressure and temperature of said working fluid; means fordirecting the low temperature, low pressure working fluid from saidexpansion valve through said evaporator to cool the second fluid by heattransfer to said working fluid; a pump; means for directing theremainder of the relatively cool, relatively high pressure working fluidfrom said condenser to said pump substantially to increase the pressureof said working fluid; a boiler; means for directing the high pressure,relatively low temperature working fluid flowing from said pump to saidboiler substantially to heat said working fluid; a pair of disk valvesmounted within said housing adjacent the opposite ends of the smalldiameter portions of said cylinder for alternately and cyclicallydirecting the high pressure, high temperature working fluid flowing fromsaid boiler to the opposed small diameter portions of said cylinder toreciprocate said free piston therein and means for directing spentworking fluid from said small diameter portions of said cylinder meansto said condenser; and means for rotating said disk valves insynchronism to control flow of working fluid alternately through thesmall diameter portions of said cylinder.
 5. The heat pumping systemaccording to claim 4 wherein the disk valves are rotated in synchronismby a shaft extending between the valves and through the free piston. 6.The heat pump system according to claim 5 wherein said cylinder forms ahermetic seal enclosing at least said free piston, said disk valves, andsaid valve rotating means.
 7. The heat pump system according to claim 4further including means responsive to the level of working fluid withinthe boiler for selectively bypassing high pressure, relatively lowtemperature working fluid flowing from the outlet of said pump to theinlet of said pump.
 8. A heat pump system comprising: a free pistonincluding a relatively large diameter portion and concentric relativelysmall diameter portions extending coaxially from the opposite ends ofthe larGe diameter portions; cylinder means surrounding the free pistonand including a central relatively large diameter portion for receivingthe large diameter portion of said free piston and opposed relativelysmall diameter portions for receiving the small diameter portions ofsaid piston; a pair of disk valves mounted in said cylinder meansadjacent to opposite ends of said small diameter portions thereof; meansfor rotating said disk valves in synchronism for alternate flow ofworking fluid into and out of the small diameter portions of saidcylinder means to reciprocate said free piston within said cylindermeans; said cylinder means forming a hermetic seal which encloses atleast said free piston, said disk valves, and said valve rotating means;a condenser; a pump; means for directing part of the working fluidflowing from said condenser to said pump substantially to pressurizesaid working fluid; a boiler; means for directing at least part of saidworking fluid flowing from said pump to said boiler substantially toheat said working fluid; means for directing spent working fluid flowingout of said small diameter portions of said cylinder means under controlof said disk valves to the condenser; an expansion valve; means fordirecting the remainder of said working fluid flowing from saidcondenser through said expansion valve and substantially to reduce thepressure and temperature of said working fluid; an evaporator for flowof low pressure, low temperature working fluid flowing from saidexpansion valve to cool a secondary fluid by heat transfer to saidworking fluid; means for alternately admitting working fluid flowingfrom said evaporator into the opposite ends of the large diameterportion of the cylinder means partially to compress the working fluid;and means for directing compressed working fluid flowing from the largediameter portion of said cylinder means to said condenser.
 9. The heatpump system according to claim 8 wherein the valve rotating meanscomprises: an induction motor including a rotor enclosed by saidcylinder means; and a shaft extending through said free piston along theaxis thereof for interconnecting said disk valves and therebymaintaining a predetermined angular phase relationship between saidvalves.
 10. The heat pump system according to claim 8 further includingmeans responsive to the pressure within the small diameter portions ofsaid cylinder at the terminus of each reciprocation of the free pistontherein for regulating the flow of high pressure, high temperatureworking fluid into the small diameter portions of said cylinder means.11. The heat pump system according to claim 10 further including meansresponsive to the level of working fluid within said boiler forrecirculating a portion of the pump output to the inlet thereof.
 12. Aheat pumping process comprising: alternately receiving low pressure,relatively warm working fluid from an evaporator in the opposite ends ofthe large diameter portion of a dual diameter, double-acting free pistonassembly and thereby partially compressing the working fluid; directingthe partially compressed working fluid from the large diameter portionof the free piston assembly through a condenser and thereby partiallycooling the working fluid; directing a portion of the partially cooledworking fluid flowing from the condenser through an expansion valve andthereby simultaneously substantially reducing the pressure of andsubstantially cooling the working fluid; directing the low pressure, lowtemperature working fluid flowing from the expansion valve through theevaporator and thereby cooling a secondary fluid; directing theremainder of the partially cooled working fluid flowing from thecondenser through a pump and thereby substantially compressing theworking fluid; directing the high pressure working fluid flowing fromthe pump through a boiler and thereby suBstantially heating the workingfluid; alternately admitting the high temperature, high pressure workingfluid from the boiler to the opposed small diameter portions of the freepiston assembly by means of rotating disk valves located at the oppositeends of the free piston assembly and thereby reciprocating the freepiston; releasing the spent working fluid from the small diameterportions of the free piston through said rotating disk valves; anddirecting the spent fluid to the condenser.
 13. The heat pumping processaccording to claim 12 wherein the steps of admitting high temperature,high pressure working fluid to the opposite ends of the small diameterportion of the free piston assembly and directing spent working fluidfrom the free piston assembly to the condenser are further characterizedby simultaneously rotating the disk valves located at the opposite endsof the free piston assembly by means of a rod extending through the freepiston and interconnecting the two disk valves.
 14. The heat pumpingprocessing according to claim 12 further characterized by the step ofregulating the rate of fluid flow from the boiler into the opposite endsof the small diameter portions of the free piston assembly in accordancewith the pressure of the spent working fluid within the small diameterportions of the free piston assembly at the end of each reciprocation ofthe free piston.
 15. The heat pumping process according to claim 12wherein the step of directing the high pressure working fluid flowingfrom the pump through a boiler is further characterized by returning aportion of the pump output to the input thereof in accordance with thelevel of working fluid within the boiler.
 16. A heat pumping processcomprising: cooling relatively high pressure, relatively warm workingfluid in a condenser; substantially reducing the pressure of and therebysubstantially cooling part of the relatively high pressure, relativelylow temperature working fluid flowing from the condenser in an expansionvalve; partially heating the low temperature, low pressure working fluidflowing from the expansion valve in an evaporator and therebysubstantially cooling a secondary fluid; partially compressing the lowpressure, relatively warm working fluid flowing from the evaporator inthe large diameter portion of a dual diameter, double-acting free pistonapparatus; directing the partially compressed, relatively warm workingfluid from the large diameter portion of the free piston apparatus tothe condenser; substantially pressurizing the remainder of therelatively high pressure, relatively cool working fluid flowing from thecondenser in a pump; substantially heating the high pressure, relativelylow temperature working fluid flowing from the pump in a boiler; rotangdisk valves at the opposite ends of the small diameter portion of thefree piston assembly and thereby cyclically admitting the hightemperature, high pressure working fluid flowing from the boiler toopposed small diameter portions of the free piston apparatus toreciprocate the free piston; rotating said disk valves at the oppositeends of the small diameter portion of the free piston assembly andreleasing spent working fluid through said disk valves from the smalldiameter portions of the free piston apparatus; and returning the spentworking fluid to the condenser.
 17. The heat pumping process accordingto claim 16 wherein the step of rotating disk valves at the oppositeends of the small diameter portion of the free piston assembly isfurther characterized by maintaining the disk valves in synchronism bymeans of a rod interconnecting the disk valves and extending through thefree piston of the free piston apparatus.
 18. The heat pumping processaccording to claim 16 wherein the step of admitting high temperature,high pressure working fluid from the boiler to the small diameterportions of the free piston apparatus is further characterIzed bymonitoring the pressure within the small diameter portions of the freepiston apparatus at the end of each reciprocation of the free piston andregulating the flow of high temperature, high pressure fluid into thesmall diameter portions of the free piston assembly in accordance withsuch pressure.
 19. A heat pump system comprising: a housing having adual diameter cylinder including a central relatively large diameterportion and concentric relatively small diameter portions extendingaxially from the opposite ends of the large diameter portion; a dualdiameter free piston including a central relatively large diameterportion received in the large diameter portion of said cylinder andrelatively small diameter portions extending from the opposite ends ofthe relatively large diameter portion into the small diameter portionsof said cylinder; an evaporator adapted to effect heat transfer betweena working fluid and a secondary fluid; means for directing low pressure,relatively warm working fluid flowing from said evaporator into therelatively large diameter portion of said cylinder partially to compressthe working fluid upon reciprocation of the free piston; a condenseradapted to effect heat transfer between said working fluid and a thirdfluid; means for directing relatively high pressure, relatively warmworking fluid from the large diameter portion of said cylinder to saidcondenser to cool the working fluid; an expansion valve; means fordirecting part of the relatively high pressure, relatively cool workingfluid flowing from said condenser through said expansion valvesimultaneously substantially to reduce the pressure and temperature ofsaid working fluid; means for directing the low temperature, lowpressure working fluid from said expansion valve through said evaporatorto cool the secondary fluid by heat transfer to said working fluid; apump; means for directing the remainder of the relatively cool,relatively high pressure working fluid from said condenser to said pumpsubstantially to increase the pressure of said working fluid; a boiler;means for directing the high pressure, relatively low temperatureworking fluid flowing from said pump to said boiler substantially toheat said working fluid; means located within said housing foralternately and cyclically directing the high pressure, high temperatureworking fluid flowing from said boiler to the opposed small diameterportions of said cylinder to reciprocate said free piston therein; meansresponsive to pressures within the small diameter portions of saidcylinder at the terminus of each stroke of said free piston forcontrolling the flow of high pressure, high temperature working fluidinto said small diameter portions of said cylinder to assure dissipationof the energy of the working fluid during each reciprocation of saidfree piston; and means located within said housing for directing spentworking fluid from said small diameter portions of said cylinder meansto said condenser.